I feel that Ineos made a mistake in estimating that 30 s would be enough. Roglic is lighter than Thomas and would have the advantage. They needed 1 minute to be sure. They needed to attack him in the mountains when he was weak. In this TT also they made lot of mistakes that cost. The salt stains on his shorts indicate too much sweating which no other riders had. Did they over warmup? Then the leisurely change of helmet and bike. Considering 50 million budget that is not good. Finally Roglic did a Pogacar to Thomas here. Obviously teams/riders are doomed to repeat the same mistakes again.
Easy to say that now. Thomas did attacked him twice. First time he gained 25 sec and 2nd time he lost 3 sec.
On stage 16 Jumbo worked all day and everything was pointing that Roglic is feeling fine and wants to attack. The moment Thomas suspect he's not that great, he attacked right a way.
On stage 18 Roglic was on the offensive, Thomas couldn't do anything.
On stage 19, Roglic also on the move, but Thomas countered at the Flamme Rouge only to lose couple of seconds.
Only thing he could maybe did is forcing major selection on Giau, trying to tyre Roglic up, but in the process he would burn his team and become vulnerable to attacks of Almeida, Caruso, Dunbar etc,
Bottom line is that Thomas is aware what kind of rider he is. He knows he's not a Pogacar to attack whenever and wherever he wants. He knows he needs to play to his strengths which is consistency and endurance, and he did just that, but it was not enough.
And he also knew he was facing a rider which may show some weakness, but also may show up as an alien.